Three-dimensional simulation of hydraulic fracture propagation height in layered formations

The prediction of hydraulic fracture (HF) propagation height is of great significance for hydraulic fracturing design and mitigating unfavorable fracture propagation. The height growth of HF in a layered formation is influenced by multiple factors, including in-situ stresses, Young’s modulus, layer interfaces, and their combined effects, in addition to the influence of stress shadows. In this work, the influence of multiple factors on HF propagation was studied using the 3D hydro-mechanically coupled lattice-spring code. Both vertical and lateral HF growth were evaluated quantitatively, and the non-planar propagation of HFs captured. Numerical modeling results show that the HF height decreases with the increment of minimum horizontal principal stress in adjoining layers. As the horizontal stress will be the major principal stress if it exceeds the vertical stress, the HF plane is gradually deflected into the horizontal plane, and the HF crosses the interface into the adjacent layers. Vertical fracture propagation is promoted in high-modulus layers and inhibited in low-modulus layers. Because of fracture tip blunting induced by the shear slip of the interface and fluid leak-off into the interface, HF propagation height is reduced. Multiple mechanisms can be considered together to describe HF propagation in a layered formation. Considering the effect of a weak interface alone, model results may show HF height containment. With a high-modulus or low-stress layer beyond the interface, the HF could cross the interface, leading to further HF height growth. Besides, the stress shadow effect is highlighted as an important mechanism in HF height containment. The HF may reorient itself to become horizontal, thereby resulting in HF height containment. The model results presented allow an improved understanding of the mechanisms of HF height containment in layered formations.